First, use DOSbox 0.65, not any older version.
Secondly: did you increase cycles? CTRL+F12 until it becomes bearable.
Or say "config -set cpu cycles=auto" (without the quotes) at the DOSbox command prompt before you run the game.
Also you can try "config -set cpu core=dynamic".
For setting these permanently, read the README. It explains how to create a config file. Then you just edit it with a text editor.
Other things to try: output=ddraw or output=opengl or output=openglnb. Also frameskip=5 as a last resort thing. All of these go into the config file.
Finally, it might be your PC is just too slow to run the game in DOSbox, which is still an emulator at the end of the day, and can never be as fast as programs running natively, even though it's got a lot closer in the new version.